Afon Hafren — known in English as the River Severn — is the longest river in Great Britain, stretching approximately 220 miles (354 km) from its headwaters in the Cambrian Mountains of mid Wales to the Severn Estuary near the M4 bridge. The river rises on the slopes of Plynlimon (Pumlumon) at an elevation of around 610 metres (2,000 feet), close to the Ceredigion and Powys border near Llanidloes. Remarkably, the source of the Afon Hafren lies just metres from the source of the River Wye on the same massif. From its origins, the river flows in a north-easterly direction through the Welsh towns of Llanidloes and Welshpool before crossing into England, where it adopts a more southerly course through Shropshire, Worcestershire, and Gloucestershire, passing through the county towns of Shrewsbury, Worcester, and Gloucester. With an average flow rate of 107 m³/s at Apperley in Gloucestershire, the Afon Hafren carries the most voluminous flow of any river in England and Wales, making it a truly significant waterway for anglers across its entire length.